It is known that an internal combustion engine of a motor vehicle is provided with a lubrication system suitable for lubricating the rotating or sliding components of the engine. The lubrication system generally comprises an oil pump driven by the engine, which draws lubricating oil from a sump and delivers it under pressure through a main oil gallery in the engine cylinder block, wherein said main oil gallery is connected via respective pipes to a plurality of exit holes for lubricating crankshaft bearings (main bearings and big-end bearings), camshaft bearings operating the valves, tappets, and the like.
In order to cool the engine pistons, most internal combustion engines are provided with an auxiliary oil gallery in the engine cylinder block, which is connected via respective pipes to a plurality of oil jets for squirting lubricating oil into an upper crankcase area towards piston surfaces. The auxiliary oil gallery is connected to the main oil gallery via a feeding line equipped with a valve for selectively open or close said feeding line.
In modern internal combustion engines, this valve is electrically driven and is commanded by an engine control unit (ECU) according to a dedicated managing strategy, thereby allowing an effective cooling of the pistons and consequently a significant fuel saving and polluting emission reduction. This electrically driven valve is commonly defined as squirters valve or Oil Piston Cooling Jets (OPCJ) valve.
In order to diagnose OPCJ valve failures, the auxiliary oil gallery, also referred as Oil Pistons Cooling Jets (OPCJ) gallery, is now usually provided with a dedicated pressure sensor, which monitors the pressure variation in the OPCJ gallery due to an electrical switching signal sent to the OPCJ valve. As a matter of fact, if the OPCJ valve is working properly, any switching signal should result in an effective switching of the OPCJ valve itself, namely an OPCJ valve opening or closure, which in turn should result in a significant pressure variation in the OPCJ gallery, so that a failure can be detected when the pressure variation does not occur.
However, the OPCJ gallery pressure sensor is an extra sensor that is installed in addition to a primary pressure sensor, which is generally located in the main oil gallery for other lubrication system managing purposes. Therefore, the OPCJ gallery pressure sensor results also an additional cost for the internal combustion engine. At least one object is to provide a new method to diagnose OPCJ valve failures. At least another object is to reach this goal with a simple, rational and rather inexpensive solution. In addition, objects, other desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.